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Cardiac Disease

Introduction

Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD has remained the leading cause of death worldwide despite the tremendous progress made in medical and surgical treatment for this disease. An estimated 17.5 million people died from CVDs in 2012, representing 31% of all global deaths. Of these deaths, an estimated 7.4 million were due to coronary heart disease and 6.7 million were due to stroke. Most cardiovascular diseases can be prevented by addressing behavioral risk factors such as tobacco use, unhealthy diet and obesity, physical inactivity and harmful use of alcohol using population-wide strategies. People with cardiovascular disease or who are at high cardiovascular risk (due to the presence of one or more risk factors such as hypertension, diabetes, hyperlipidemia or already established disease) need early detection and management using counseling and medicines, as appropriate.

Types of Cardiac Disease

Cardiovascular diseases (CVDs) are a group of disorders of the heart and blood vessels (Figure 1):

1. Peripheral Arterial Disease

The prevalence of peripheral arterial disease (PAD) in the general population has been estimated to approach 12% in the United States. About one-third of patients with coronary artery disease also suffer from PAD. The most common cause of PAD is arteriosclerosis obliterans – segmental arteriosclerotic narrowing or obstruction of the lumen of the arteries supplying the limbs. The lower limbs are involved more frequently than the upper limbs. Although not life threatening, this condition causes considerable pain and disability.

2. Coronary Artery Disease

Coronary artery disease (CAD) is a group of diseases that includes: stable angina, unstable angina, myocardial infarction (MI), and sudden coronary death. It is within the group of cardiovascular diseases of which it is the most common type. A common symptom is chest pain or discomfort which may travel into the shoulder, arm, back, neck, or jaw. Occasionally it may feel like heartburn. Usually symptoms occur with exercise or emotional stress, last less than a few minutes, and gets better with rest. Shortness of breath may also occur and sometimes no symptoms are present. The first sign is occasionally a heart attack. Other complications include heart failure or an irregular heartbeat.

3. Cardiomyopathy

Cardiomyopathy (heart muscle disease) is the measurable deterioration (enlarged or abnormally stiff or thick heart) for any reason of the ability of the myocardium (the heart muscle) to contract, usually leading to heart failure or arrhythmia. Common symptoms include dyspnea (breathlessness) and peripheral edema (swelling of the legs). Those with cardiomyopathy are often at risk of dangerous forms of irregular heart rate and sudden cardiac death. The most common form of cardiomyopathy is dilated cardiomyopathy. Although the term "cardiomyopathy" could theoretically apply to almost any disease affecting the heart, it is usually reserved for "severe myocardial disease leading to heart failure."

4. Cardiac Arrhythmia

Cardiac arrhythmia, also known as cardiac dysrhythmia. Both terms describe the clinical presentation of abnormal cardiac electrical impulse formation or impulse conduction through cardiac muscle. These can result in either too slow or too fast heart rhythms. Many types of arrhythmia have no symptoms. When symptoms are present these may include palpitations or feeling a pause between heartbeats. More seriously there may be lightheadedness, passing out, shortness of breath, or chest pain. While most types of arrhythmia are not serious but some predispose a person to complications such as stroke or heart failure. Others may result in cardiac arrest. Arrhythmias can occur at any age from the developing fetus through adulthood. Developmental alterations of the cardiac conduction tissue, genetically inherited changes of myocardial cellular ion membrane properties, and associated structural congenital heart anatomical defects can all play a role.

5. Atherosclerosis and Hyperlipidemia

Atherosclerosis occurs as a result of an orchestrated process encompassing vascular endothelial dysfunction, lipid accumulation, aberrant inflammatory responses and vascular cell proliferation and migration. These events underlie the progressive narrowing and thickening of the arteries with a possibility of thrombus formation and vessel occlusion leading to stroke or heart attack. Atherosclerosis is asymptomatic for decades because the arteries enlarge at all plaque locations, thus there is no effect on blood flow. Even most plaque ruptures do not produce symptoms until enough narrowing or closure of an artery, due to clots, occurs. Signs and symptoms only occur after severe narrowing or closure impedes blood flow to different organs enough to induce symptoms. Most of the time, patients realize that they have the disease only when they experience other cardiovascular disorders such as stroke or heart attack. These symptoms, however, still vary depending on which artery or organ is affected.

6. Hypertension

Hypertension is defined as a persistence increase in blood pressure above the normal range of 120/80 mm Hg. The prevalence of hypertension increases with advancing age. The persistent and chronic elevated arterial pressure causes marked pathological changes in the vasculature and heart. The blood pressure (BP) of ≥140/90 mm Hg is a criterion by which the risk of hypertension-related cardiovascular disease is high enough and needs immediate medical attention. Hypertension is a major risk factor for coronary artery disease and its complications, heart failure, stroke, and renal insufficiency. Hypertension is preventable by medication and significant lifestyle modification.

7. Valvular Heart Disease

Valvular heart disease (VHD) is any disease process involving one or more of the four valves of the heart (the aortic and mitral valves on the left and the pulmonary and tricuspid valves on the right). VHD is a common cardiac condition with a big impact on healthcare economics. The incidence of VHD had been increasing over the past few decades, likely due to aging population. Rheumatic heart disease (RHD) is still a major etiologic factor for the development of VHD worldwide, whereas degenerative valve disease is likely the most common etiology of VHD in developed countries. The prevalence of the VHD increases from 0.7 % in people <45 years to 13 % in people over 75 years. This translates to a significant public health burden. Thus, a physician should be well versed in obtaining a thorough history and performing a complete physical examination, understand the appropriate diagnostic testing to accurately diagnose the severity of valve disease, and apply timely therapeutic options that are available with a clear understanding of their effect on morbidity and mortality.

8. Heart Failure

Heart failure (HF) is an important healthcare issue because of its high prevalence, mortality, morbidity, and cost of care. It is estimated that more than eight million Americans will have HF by 2030. HF incidence increases with age, rising from approximately 20 per 1,000 individuals 65–69 years of age to >80 per 1,000 individuals among those >85 years of age. Ischemic heart disease, hypertension, and valvular heart disease are the most common causes of HF. Less common causes include diabetes; genetic cardiomyopathies and muscular dystrophies; autoimmune and collagen vascular diseases; toxic cardiomyopathies, including alcohol or illicit drugs such cocaine; chemotherapy- induced cardiomyopathies (e.g., Adriamycin); myocarditis and viral cardiomyopathy; postpartum cardiomyopathy; tachycardia-mediated HF; infiltrative disorders, such as sarcoidosis, hemochromatosis, and amyloidosis; high-output states; and stress-induced (takotsubo) cardiomyopathy.

9. Rheumatic Heart Diseasee

Rheumatic heart disease (RHD) is a chronic disease which heart muscles and valves damage due to rheumatic fever caused by Streptococcus pyogenes a group A streptococcal infection. RHD is characterized by repeated inflammation with fibrinous repair. The cardinal anatomic changes of the valve include leaflet thickening, commissural fusion, and shortening and thickening of the tendinous cords. It is caused by an autoimmune reaction to Group A β-hemolytic streptococci (GAS) that results in valvular damage.

10. Congenital Heart Disease

Congenital heart disease is a problem in the structure of the heart that is present at birth. Signs and symptoms depend on the specific type of problem. Symptoms can vary from none to life-threatening. When present they may include rapid breathing, bluish skin, poor weight gain, and feeling tired. It does not cause chest pain. Most congenital heart problems do not occur with other diseases. Complications that can result from heart defects include heart failure.

Figure 1. Types of heart disease and risk factors.

Biomarker of Cardiac Disease

Biochemical markers play a crucial role in accurate diagnosis of cardiac disease and, more importantly, for assessing risk and directing appropriate therapy that improves clinical outcome. Development and utilization of biomarkers has evolved substantially over the past three decades.

1. Biomarkers of Myocardial Necrosis

Biomarkers have provided important information for the clinical assessment of patients with suspected myocardial infarction (MI) patients since the early 1950s. As displayed in Fig. 2, utilization of biomarkers has evolved substantially over the past 30–40 year. Biomarkers were previously considered to be one of the three important variables, along with changes on the electrocardiogram (ECG) and clinical signs and symptoms, necessary for the diagnosis of MI as defined by the World Health Organization (WHO) in 1979. The biomarkers cardiac troponin T (cTnT) and I (cTnI) are now designated as surrogates for necrosis and MI when elevated in the setting of acute cardiac ischemia, according to the consensus document of the European Society of Cardiology (ESC) and the American College of Cardiology (ACC).

Assessing patients with suspected acute coronary syndrome (ACS) remains problematic even though there is a growing armamentarium of diagnostic and prognostic tests as well as continued improvement in the sensitivity and specificity of existing methods. Percentage of inadvertent discharges of patients thought to be at low risk of ischemia but later found to have an ACS remains unacceptably high, at 4 to 5%, of whom about half have an acute myocardial infarction (AMI) and the remainder unstable angina. This limitation adversely impacts clinical outcomes, as well as the cost of health care and underlies the need for exploration of new strategies aimed at rapidly identifying those patients who present with ACS but lack traditional diagnostic findings, including definitive electrocardiogram (ECG) findings, and/or biochemical evidence of necrosis. Biomarkers hold promise to be valuable in this regard. The understanding of the pathophysiology of ACS provides a myriad of opportunities for diagnostic and prognostic testing within this pathophysiological construct (Fig. 3). However, assessment at different stages or of different contributors to the genesis of ACS is likely to have different implications for prognosis and therapy.

Heart failure is characterized by an ongoing inflammatory response. The inflammation hypothesis, as it currently stands, suggests that heart failure progresses because certain inflammatory mediators such as inflammatory cytokines are activated following the initial myocardial injury and continue to exert deleterious effects on the heart and circulation contributing further to progression of heart failure and left ventricular dysfunction. Inflammatory biomarkers in heart failure comprise a portfolio of markers that include biologically active molecules, such as proinflammatory cytokines and chemokines that are involved in the pathogenesis and progression of heart failure, and others that reflect severity of inflammation such as C-reactive protein or erythrocyte sedimentation rate. Most of these biomarkers correlate with severity of disease, prognosis, and clinical outcomes in heart failure.

There are several risk factors for heart diseases. While the individual contribution of each risk factor varies between different communities or ethnic groups the overall contribution of these risk factors is very consistent. Some of these risk factors, such as age, gender or family history, are immutable; however, many important cardiovascular risk factors are modifiable by lifestyle change, social change, drug treatment and prevention of hypertension, hyperlipidemia, and diabetes.

1. Age

Age accounts for the most important risk factor in developing cardiovascular or heart diseases, with approximately a tripling of risk with each decade of life. Multiple explanations have been proposed to explain why age increases the risk of cardiovascular/heart diseases. One of them is related to serum cholesterol level. In most populations, the serum total cholesterol level increases as age increases. In men, this increase levels off around age 45 to 50 years. In women, the increase continues sharply until age 60 to 65 years. Aging is also associated with changes in the mechanical and structural properties of the vascular wall, which leads to the loss of arterial elasticity and reduced arterial compliance and may subsequently lead to coronary artery disease.

2. Gender

Men are at greater risk of heart disease than pre-menopausal women. Coronary heart diseases are 2 to 5 times more common among middle-aged men than women. One of the proposed explanations for gender differences in cardiovascular diseases is hormonal difference. Among women, estrogen is the predominant sex hormone. Estrogen may have protective effects through glucose metabolism and hemostatic system, and may have direct effect in improving endothelial cell function. The production of estrogen decreases after menopause, and this may change the female lipid metabolism toward a more atherogenic form by decreasing the HDL cholesterol level while increasing LDL and total cholesterol levels.

3. Tobacco

Cigarettes are the major form of smoked tobacco. Risks to health from tobacco use result not only from direct consumption of tobacco, but also from exposure to second-hand smoke. Approximately 10% of cardiovascular disease are attributed to smoking; however, people who quit smoking by age 30 have almost as low a risk of death as never smokers.

4. Physical Inactivity

Insufficient physical activity is currently the fourth leading risk factor for mortality worldwide. The risk of ischemic heart disease and diabetes mellitus is reduced by almost a third in adults who participate in 150 minutes of moderate physical activity each week (or equivalent). In addition, physical activity assists weight loss and improves blood glucose control, blood pressure, lipid profile and insulin sensitivity. These effects may, at least in part, explain its cardiovascular benefit.

5. Diet

High dietary intakes of saturated fat, trans-fats and salt, and low intake of fruits, vegetables and fish are linked to cardiovascular risk. Frequent consumption of high-energy foods, such as processed foods that are high in fats and sugars, promotes obesity and may increase cardiovascular risk. The relationship between alcohol consumption and cardiovascular disease is complex, and may depend on the amount of alcohol consumed. There is a direct relationship between high levels of alcohol consumption and risk of cardiovascular disease. Drinking at low levels without episodes of heavy drinking may be associated with a reduced risk of cardiovascular disease. Overall alcohol consumption at the population level is associated with multiple health risks that exceed any potential benefits.

Prevention of Cardiac Disease

All coronary patients should be advised and have the opportunity to access a comprehensive cardiovascular prevention and rehabilitation programme, addressing all aspects of lifestyle-smoking cessation, healthy eating and being physically active-together with more effective management of blood pressure, lipids and glucose. To achieve the clinical benefits of a multidisciplinary and multifactorial prevention programme we need to integrate professional lifestyle interventions with effective risk factor management, and evidence based drug therapies, appropriately adapted to the medical, cultural, and economic setting of a country. The challenge is to engage and motivate cardiologists, physicians and health professionals to routinely practice high quality preventive cardiology and a health care system which invests in prevention.